The present invention relates to cooling engines in general and, more particularly, to cooling engines having a free, gas-driven displacer.
Traditionally, free displacer, i.e., free piston cooling engines, work well thermodynamically, but lack sufficient reliability over a long period of time for them to be commercially successful against the currently available mechanical driven cooling engines. The problem with a free, gas-driven displacer is controlling the motion of the displacer at the top dead center and the bottom dead center of its cycle. In order to achieve high thermodynamic efficiency, the volumes at top dead center (TDC) and bottom dead center (BDC) should approach zero. With free displacer machines, this objective is very difficult to achieve without collisions taking place between the displacer and cylinder containing the displacer.
It is, accordingly, a general object of the present invention to provide both a method and apparatus for snubbing the movement of a free, gas-driven displacer in a cooling engine.
It is a specific object of the invention to utilize magnetic repulsion forces to provide the desired snubbing action for the free, gas-driven displacer.
It is another object of the invention to control the snubbing of a free, gas-driven displacer on a non-linear basis that varies inversely with the distance between the displacer and the ends of the displacer containing cylinder at TDC and BDC.
It is a feature of the invention that the method can be practiced and the apparatus constructed utilizing relatively inexpensive and commercially available magnetic components.
It is another feature of the invention that the "bang - bang" operation of conventional free, gas-driven displacer machines is eliminated with a concomittant increase in the reliability and longevity of such cooling engines.